Hi all

I have released firmware 1_00_017 at

The most important features are the AGC and S-meter.?

S-meter: it appears in the 3 characters to the right of the mode indicator character, when S-meter is enabled. The 15 vertical bars are worth 6dB each and therefore correspond to levels from S0 to S9 (9 bars) and?on up at S9+6dB, S9+12dB etc to S9+36dB when all three are full solid. The scale is calibrated in real decibels, but the accuracy of S0 relative to an actual signal input depends on the level of the gain setting you set for various bands in the Band Configuration terminal menu.?

AGC: it's a quite complex sub-system and I have documented the concepts and parameters in the 1_00_017 operating manual at , section 5.21 pages 52-57 inclusive. Briefly...?

AGC operates in the decibel domain, not linear. There is an AGC threshold below which AGC does not operate, it's a parameter specified in S-meter units. There's an impulse noise filter whose duration is configurable. The AGC slope is configurable so you can adjust it to your taste, you can have a gentle AGC action where strong signals are louder than weak ones, or an aggressive one where the AGC system makes everything the same volume. Hang time and recovery rate are also configurable.?

The AGC system creates an audio sample delay line, which it analyzes for impulse peaks then applies the calculated AGC gain (attenuation) to the sound samples in the delay line. The action of the AGC is therefore effectively instant; no matter how strong the incoming signal, the time taken for the AGC to react to it and protect your ears is always zero,?no piece of strong signal reaches your ears. The length of the delay line is configurable and needs to be a minimum 1.3ms for CW. SSB has a lower minimum audio frequency so a longer delay line is required; the maximum configuration is 6ms which would be able to handle signals down to 83 Hz. Either way, it's a very small latency.?

The S-meter also has a configurable "AGC action" display; if enabled, the S-meter looks like the Power/SWR meter function (during transmit) with two bars. The upper bar is the S-meter and the lower bar is the AGC action, with a configurable number of dB per pixel. It just helps you to see when AGC is active.?

The S-meter configuration parameters were moved to their own sub-menu under the Display/controls menu, and include an S-meter update interval parameter.?

I created a short demonstration YouTube video? . In this video I used a QCX, with about 150cm of wire attached to the antenna port, to generate a strong CW test signal. The BS170s in the QCX are toasted so this just produces very little actual power output but of course we are in close proximity, so the signal level "received" by the QMX is enormous, approx S9+30dB. In the video you can see heavy clipping when the AGC is off, which would no doubt generate a gigantic headache if you had earphones on; when I switch AGC on the signal is reduced to a comfortable S9 level.?

I also tested the QMX with AGC on 40m at night, tuning around for strong signals with and without AGC and I believe it is highly effective.?

The system is highly configurable, I suspect it may be TOO configurable; I will look forward to your feedback and suggestions on how it may be improved, and in particular it may be possible to remove some of these configurations, or derive or calculate them. The attached screenshot shows the configuration I used for the video. I must say though that it does not appear to be a delicate act, balancing parameters carefully; it seems generally to be very effective and insensitive to the exact settings.?

I do highly recommend though that you read the operating manual pages 52-57 carefully; initially all the parameters will be zero and you need to set it up carefully, before enabling AGC. At the moment there are no default values. So let's see.?

Other than that, I also added an LPF sweep tool (see example attached), which was discussed some time ago here. It "transmits" at 1/4 full power, into a dummy load (DO connect a dummy load!) while sweeping the transmit frequency, and plots the measured power output, after conversion to dB and normalizing the center frequency measurement as 0dB. It's indicative only, but quite interesting to see and educational, perhaps useful for debugging too.?

Plus a couple of bug fixes; change list is:

1. Bug fix: '5351 synth code for setting TX params could lock up in some circumstances
2. New LPF Sweep application in the terminal
3. Added S-meter
4. Added AGC implementation and supporting configuration menu parameters
5. Bug fix: Parameter corruption (incl IQ Mode setting lost) in Digi config menu

So that's my week's work here.?

73 Hans G0UPL

That did the trick! I looked closely at the joints for L1 and L2 and noticed that one of L2's? pads (nearest IC3) wasn't fully flowed around the wire. It passed the continuity check when I assembled the board, but it must have been marginal. I reflowed it and the others on 80M just to be sure, and am now getting 7.1w on 80m.

Thank you!

John K1QLN

Hi All,
I have a rev 3a QDX (80-20 model, firmware 1.10) that I built back around 10/2022. I used it more or less continuously for 6mo after building it, with great results. I wrapped T1 for 12v and usually ran it from my bench supply at 13.8-14.4v. I never had issues with heat - my shack is in the basement and is rarely over 60-65F, but perhaps this is the root of my problem?

In any case, I set it up again this morning and while going through the bands I discovered that 80M doesn't transmit at all. The LED pulses, but the meter on my ATU registers no output power. The rest of the bands seem fine - 5.5w on 20M, 7.3w on 30M, 5.9w on 40M, and 7.6w on 60M, tested using the built in transmitter tester. I see the same results using the tune button in WSJT-X.??

I shot a quick video here:

And have photos of the board here (I don't see anything wrong, but perhaps someone else will) -?



Any recommendations for things to check or test? I have a pretty standard complement of radio/lab gear to work with.

Thanks & 73s,
John K1QLN

Hi all

QMX kits: FINALLY after some UNNECESSARY delays and FedEx FRUSTRATION Arrrggghhhh we finally got the 8 boxes of 1,000 QMX Rev 3 boards yesterday afternoon. My team are building two for testing right now. I don't expect any issues. My team are also flashing the bootloaders. The other components and enclosures are already prepared. Subject to successful testing we'll begin shipping the pending QMX kit orders today; there are around 250 orders pending so it will not happen instantly, but I hope we can clear the backlog within a week.?

QMX Assembled (and QCX-series, QDX-series): See attached: we are making good progress on reducing the size of the backlog. The assembled radio waiting list is here: and I update it normally every weekday unless I have a brain lapse. It currently stands at 815 orders, down from a peak of 906.?

Any urgent requests, please let me know.?

We have two new employees starting on Monday. Which reminds me I need to order some new soldering irons and solder today otherwise that's not going to help us much, is it :-/? ?And we have a carpenter building two new 90 x 270cm tables for our 4'th room up here in QRP Labs towers.?

73 Hans G0UPL

I was able, using the wire jumper, to roll back to 016 Firmware, and my darling QMX appears happy again. It's nice that one only needs to remove the 2 bottom screws on each side of the enclosure to pop the bottom cover off (no need to remove knobs and disassemble otherwise).



Roy - KI0ER